Effective Improvement of Thermodynamics and Kinetics of BiVO<sub>4</sub> Photoanode via CuI for Photoelectrochemical Water Oxidation
Yuan Guan, Zheng Shen, Xinyi Gu, Dayu Wu, Shaomang Wang, Zhongyu Li, Shicheng Yan, Zhigang Zou
Abstract
The preparation of durable and efficient photoanodes for photoelectrochemical water oxidation is of great importance in promoting the development of green hydrogen production and artificial photosynthesis. Here, n-type BiVO 4 was combined with p-type CuI to construct a CuI/BiVO 4 (CIB-1) p–n heterojunction photoanode. The composite photoanode effectively overcame the drawbacks of BiVO 4, such as low separation and injection efficiency of photogenerated electron–hole pairs. As a result, the CIB-1 had the highest photocurrent density of 1.98 mA cm –2, which was 2.5 times higher than pure BiVO 4 with 0.79 mA cm –2 at 1.23 V (vs RHE) under AM 1.5G light irradiation. The CIB-1 had a lower Tafel slope of 23.2 mV decade –1 compared to 47.9 mV decade –1 for BiVO 4, so the water oxidation kinetics was remarkably advanced over CuI/BiVO 4 . Based on DFT calculations, the OER overpotential of 0.480 V for CuI/BiVO 4 was significantly lower than that of 1.546 V for BiVO 4 due to the lower free energy from OH – to oxygen over CuI/BiVO 4 compared to BiVO 4 .